The present invention relates to a method and device(s) for attaining increased data rates for Cellular Digital Packet Data (CDPD) services over a cellular telephony network. Increasing demand is anticipated for higher bandwidth packet data services to support the mobile Internet. Although Cellular Digital Packet Data (CDPD) is an established and growing packet data standard that provides extensive coverage in the United States and Latin America, the user data rate is limited to approximately 10 kbps.
The present invention increases the data rate approximately two-fold for CDPD by using an alternate modulation technique. Existing CDPD systems use Gaussian Minimum Shift Keying (GMSK) modulation to provide approximately 10 kbps of user data in a cellular environment. GMSK was originally selected as the modulation technique because, at the time, use of low cost non-linear power amplifiers in the mobile terminal was important. The low cost of non-linear power amplifiers is generally no longer a factor in mobile terminal manufacturing.
The present invention increases the CDPD data rate between a mobile terminal and a basestation in a digital cellular mobile communications system. The present invention uses a different modulation technique for encoding and decoding TIA/EIA-136 frames with respect to CDPD. Rather than using GMSK, the present invention uses the same modulation technique as the digital speech air interface. Specifically, the encoding step is comprised of constructing a CDPD block, assembling an TIA/EIA-136 frame leaving the data fields of the frame empty, and populating the data fields with CDPD block data. The assembled TIA/EIA-136 frame is then transmitted using existing transmission software within the mobile terminal or basestation. The decoding step is comprised of receiving the TIA/EIA-136 frame which has CDPD data in the data fields and re-assembling the CDPD block by extracting the CDPD block data from the TIA/EIA-136 frame""s data fields. Once re-assembled, the CDPD block is forwarded to existing CDPD upper layer software within the mobile terminal or basestation for further processing.
The present invention pertains to communications between mobile terminals and basestations in a digital cellular communications system. Thus, when CDPD blocks are encoded in a mobile terminal they are sent to and decoded in the basestation. Similarly, when CDPD blocks are encoded in a basestation they are sent to and decoded in the mobile terminal.